Discoveries

Soil Science in Seconds

By: Hannah Fields

If you've ever watched Star Trek, you'll be familiar with the scanner they use when
visiting a new planet to test its environment. Even if you're not a Star Trek fan,
a scanner that can test the environment and give you a report in seconds sounds like
the perfect tool. But, that's all science fiction, right? Not quite.

Dr. David C. Weindorf using PXRF to scan subsoil cores on the Southern High Plains.

The two instruments used in Weindorf's research are the visible and near-infrared
diffuse reflectance spectroscopy (VNIR-DRS) and the portable x-ray fluorescence spectrometry
(PXRF). Both are available commercially and used extensively in Weindorf's lab.

"What our technology seeks to do is to take these two instruments and put them together
so that when you scan vegetation, soil, or liquid, you're getting both of those scans
conducted simultaneously," Weindorf said. "That doesn't mean in every scan you're
going to use data from both instruments, but for a lot of applications we do use data
from both instruments."

The VNIR-DRS works very well when measuring levels of moisture, carbon, pesticides,
arsenic, organic chemicals, and the like in soil. Not only is the VNIR-DRS a useful
tool in a lab setting, but it has also been essential in measuring the petroleum hydrocarbon
levels in soils near oil spills. For example, Weindorf and his team were called to
the Louisiana coast right after the Deepwater Horizon spill in 2010. Using the VNIR-DRS,
they were able to demonstrate to the Coast Guard the level of contaminants left by
the spill.

Using PXRF to scan for heavy metals in polluted soils of an abandoned smelting site
in Baia Mare, Romania. Read the publication >>

The PXRF, on the other hand, is like chemistry in a toolbox. When used to scan soil,
it can return measurements of around 25 different elements in 60 seconds. These elements
vary from essentials needed for soil fertility to pollutants like lead and mercury.
When used on vegetation, the PXRF can't read nitrogen levels directly, but can read
all other essential elements such as phosphorous, potassium, copper and zinc. Combine
that technology with the VNIR-DRS, Weindorf says, and the information goes from good
to great.

"One of the papers that we published a few years ago showed that by combining those
technologies we can in fact measure nitrogen in the soil to get that most important
plant essential nutrient quantified as well," Weindorf explained.

Information gathered by these combined technologies isn't just essential to researchers,
but to everyday society, especially those who are at risk of being exposed to heavy
metals. This exposure, Weindorf explains, comes in two forms: acute and chronic .
Acute exposure happens in major instances like oil spills and, while dangerous, it's
chronic exposure that is a greater threat to the environment and people alike.

"There are small amounts of elements people are exposed to daily, such as drinking
out of a water fountain that might have polluted water or getting water out of a polluted
well," Weindorf said. "It's nothing you can see or smell or taste, but you're putting
that into your body."

The technology itself doesn't clean contaminated water or soil, but it's a much-needed
tool to identify areas of pollution before a specialist is called in to clean those
areas. With a portable instrument such as these it would be possible for areas to
be assessed on site and move the cleaning process forward more quickly.

When measuring levels in soil, water, and vegetation, Weindorf and his team must take
readings with the VSNIR-DRS and PXRF separately and then combine them using statistical
algorithms. It is their goal to incorporate both technologies into one singular instrument,
and they are currently speaking with several companies about making this a possibility.

The main hurdle to clear with the creation of this technology will be the cost. According
to Weindorf, it will cost around half a million dollars or more to create the initial
prototype instrument. That instrument will then need to be tested and tweaked before
a final product is ready to be scaled down for production. Once ready for production,
the cost per unit will come down significantly.

"Our target price would be $75,000 per unit," Weindorf said. "It sounds like a lot
of money, but when you consider the accuracy and speed in which we are able to produce
these results, and the fact that a single analyst could run 200 samples per day, you're
saving $100 to $200 per sample."

However, if researchers choose to stick with traditional laboratory analysis, Weindorf
says this technology can be used to refine analysis of samples from a potentially
polluted area. For example, for every 100 samples taken, only five may have pollutants.
Instead of processing all 100 samples, they can be scanned with the VSNIR-DRS/PXRF
technologies and identify the five polluted samples quickly. Those five samples can
then be taken to the lab and processed, saving both time and money.

Oil pollution at a West Texas production facility with hydrocarbon levels determined
by VisNIR DRS. Read the publication >>

The technology was just awarded its first patent, and Weindorf and his fellow colleagues
have a positive outlook for its future.

"We feel that this is really an emergent technology," Weindorf said. "Another important
development was a second (unaffiliated) research group at University of Sydney that
have tested this combined technique and said that they highly recommend these types
of combined approaches. We have an independent validation. Our research groups are
continually pushing each other to new discoveries; it's back and forth in a good way."